Biochemical and genetic studies have indicated a role in DNA metabolism for the E. coli DNA-binding protein (SSB). Studies on the physiology of mutants defective in this protein have been initiated and additional mutants are being sought following mutagenesis of the chromosomal DNA encompassing the structural gene for SSB. Mutants of T7 defective in genes 2.5 and 2.8 will be obtained in vitro, followed by transfection into repair-deficient hosts. Mutants will be analyzed by restriction enzyme digestion and possibly DNA sequencing and their physiological defects studied in various mutant hosts. The DNA sequence of a previously characterized mutant, R9 is currently being determined.